1. Field of the Invention
This invention relates generally to an apparatus and method for transmitting information from one location to another and in particular to a portable satellite communications system for teleconferencing capable of digitizing, compressing, demultiplexing and transmitting video information from a first location, and receiving, multiplexing, decompressing and viewing the video signal at a second location.
2. Description of Related Art
A news team frequently has to transmit a video clip of a news story at some remote location back to a home television station 14. Typically, the news team accomplishes this by either using their own earth station with a satellite dish and uplink electronics or renting such an earth station from a third party. Often, however, the television station cannot afford such an earth station or none is available from a third party and consequently the news team must rely on a nearby government ministry-owned satellite earth station.
FIG. 1A shows a truck 10 with a satellite dish 16 which together serve as a point-of-origin independent work station 14. In order to be point-of-origin independent, work station 14 must use the C or Ku-band and consequently the diameter of dish 16 must be at least 10 to 15 meters. Truck 10 contains all uplink electronics required to transmit microwave signals in the C or Ku band, this equipment modulates a video signal onto a microwave signal and then amplifies and transmits the microwave signal to a satellite 20 typically owned by some government agency. That government agency is not necessarily associated with the country in which the earth station is located. The microwave signal is then downlinked to another large microwave dish 24 at television station 28 where it can be broadcast live to a surrounding area or taped for broadcast at a later time. Alternatively, local television station 28 can retransmit the video clip from dish 24 to another television station 29 having its own dish 30 with a diameter of about 8-12 feet. A local television station can then rebroadcast the video clip to its local viewers using dish 30 or broadcast tower.
This process has a variety of drawbacks. In addition, earth station 14 is very large, heavy and has expensive uplink electronics. For example, earth station 14 can weigh several tons and consequently shipping such a system can itself become very expensive. Also, truck 10 with uplink electronics and large dish 16 can require 6 to 8 men to assemble and operate. In addition, earth station 14 can cost several hundred thousand dollars to own, or tens of thousands of dollars to rent on a per day basis. Also, in order to operate earth station 14, the news team must obtain a license from the country in which earth station 14 is located. First, since earth station 14 must be shipped to the local country, it also has to pass through that local country's custom office.
Even after all of the above drawbacks are overcome, the news team cannot send the video clip from earth station 14 to television station 28 until several more steps have been performed. First, earth station 14 must contact the appropriate government agency which operates satellite 20 and prebook a specific time period during which the video clip will be transmitted from earth station 14 television station 28. In addition, earth station 14 and television station 28 both know and use the protocol required by the particular agency or government which controls satellite 20. Moreover, since the time of transmission via satellite 20 must be prebooked, the uplink will fail if the news team does not have the taped news clip ready. Also, despite its size and complexity, earth station 14 does not typically contain equipment capable of editing the video clip before it is transmitted to television station 28 via satellite 20.
The above scenario can be described as a "best case" scenario since it was assumed that the television station has its own satellite dish 24 and can rent or own an earth station 14. This situation becomes even more complicated and even impossible if, for example, television station 28 has to rely on transmitting the video clip out of the country even using that country's government satellite earth station as shown, for example, in FIG. 1B. In particular, FIG. 1B shows a government satellite earth station 40 with a large C or Ku dish 44 which uplinks C or Ku microwaves to satellite 20 which in turn downlinks these microwave signals to a large microwave dish 24 of television station 28. In this scenario, transmission from earth station 40 must be prebooked with the local government in addition to prebooking a transmission time slot with the government or agency which operates satellite 20. (These two governments are likely not the same.) Moreover, since the local government operates earth station 40, it can censor all such news clips and allow only those news clips or sections of news clips to be transmitted with which the government agrees. Furthermore, many countries will not have such a satellite earth station. Consequently, those television stations which do not have access to an earth station similar to earth station 14 in FIG. 1A must hand carry or mail the video clip to television station 28 or to another country which does have an earth station 14. Hence, by the time the video clip arrives at television station 28, the news it contains is old.
In addition to the above difficulties associated with uplinking a microwave signal to satellite 20, downlinking from satellite 20 to earth station 28 may involve one or more hops as shown in FIG. 1C. In particular, FIG. 1C shows microwave signals uplinked from either earth station 14 or governmental earth station 40 to satellite 20 which in turn must be downlinked (due to the location of satellite 20) to a first earth station 50 located, for example, in Europe. First earth station 50 must turn uplink to a second satellite 20 which in turn downlinks to second earth station 28. During this process, the protocol of each link must be complied with. This creates an even greater burden on the news team.
Teleconferencing technology like news gathering and broadcasting technology involves transmitting video signals from one location to another. However, teleconferencing differs from news gathering in that news gathering typically involves transmitting high quality video images from a first location receiving that information at a second location, whereas teleconferencing involves both transmitting and receiving video images at each of the first and second locations albeit not necessarily video images of broadcast quality.
FIG. 2 shows a first building 200 and a second building 240 interconnected via a high speed digital data network 250 such as (ACUNET) or integrated services digital network (ISDN). These networks are capable of transmitting digital information at rates of 64 kilobits/second (kbps) or in some cases 128 kbps. Network 250 must include a signal routing center 260 (typically owned and operated by a telephone company) and data lines 264 and 268 interconnecting teleconferencing equipment 274 in building 200 to teleconferencing equipment 278 in building 240. Signal routing system 260 can include a variety of satellite, fiber optic and standard hardwired links.
Teleconferencing equipment 274 and 278 must be capable of transmitting and receiving audio/video signals in real time. In order to do this, data lines 264 and 268 must be capable of transmitting more than the standard telephone line audio bandwidth of 9.6 kbps. Consequently, standard telephone lines cannot be used to interconnect teleconferencing equipment 274 to teleconferencing equipment 278.
ACUNET or ISDN interconnections can transmit at high enough bit rates to enable interconnection of teleconferencing equipment. However, high speed digital (HSD) lines or ISDN lines have been installed in only a few cities throughout the United States and only in the main business districts of those cities. Moreover, only selected buildings within those main business districts have been hard wired with high speed data lines 264 and 268. Also, installation of such high speed data lines is a long and expensive process.